What are the two types of bonds that hold hair together?

The correct answer identifies hydrogen bonds and disulfide bonds as the two primary types of bonds that hold hair together, which is vital for understanding hair structure and chemistry in cosmetology.

Hydrogen bonds are weak, temporary attractions that occur between the water molecules and the hair's protein structure. These bonds are responsible for the hair's ability to be reshaped when wet and return to its original form as it dries. This property is crucial when styling hair, as it allows for various techniques like curling or straightening.

Disulfide bonds, on the other hand, are strong, permanent bonds formed between the sulfur atoms in the amino acids of hair proteins, specifically cysteine. These bonds provide integrity and strength to the hair structure. When chemicals (like those used in perming or relaxing) are applied, they can break and reform these disulfide bonds, enabling lasting changes to the hair's shape and texture.

Understanding these bonds helps hairstylists make informed choices about chemical treatments and styling techniques, as the strength and behavior of hair largely depend on the balance between these types of bonds.